Echo PB-755SH leaf blower dies when throttle opened

Hello,

I have an Echo PB-755SH leaf blower. I received it second hand as a gift, but it has only been used a handful of times.

I can start the blower fine, and it idles without any trouble, but when I open the throttle beyond about 20%, it starts sputtering and dies unless I lower the throttle back down.

Since I have owned it (3 months), I have used it probably 5 times. The first time I used it it worked perfectly. Second time I experience this issue. Last 3 or 4 times it has been inconsistent, but now the problem is always present.

I'm new to small engine maintenance, but have done some research. Here are the facts:
I am using treated fuel with the correct oil/gas mixture.
I replaced the fuel filter just in case that was the problem.
I replaced the spark plug in case that was the problem.
I have checked the air filter and spark arrestor screen - all clear.

Any ideas before I have to take it in to the shop?

Thanks!

Echo PB-755SH leaf blower dies when throttle opened